1. Technical Field
The present disclosure relates to a turbomachine.
2. Description of the Related Art
Conventionally known turbomachines include a thrust bearing, which supports an axial load (thrust load) resulting from differences in pressure between the surfaces of an impeller thereof, and a radial bearing, which supports a radial load. Some turbomachines include an angular bearing, which supports the thrust load and the radial load. As a bearing for a rotation shaft, a bearing having a tapered shape is known.
As illustrated in FIG. 12, Japanese Unexamined Patent Application Publication No. 62-13816 discloses a turbocharger 300 including a turbine 302, a rotation shaft 303, a compressor wheel 304, a collar 306, a bearing 307a, and another bearing 307b. The rotation shaft 303 includes a tapered portion 305 gradually increasing in diameter from a middle section of the rotation shaft 303 toward the turbine 302. The collar 306 has a tapered shape gradually increasing in diameter from the middle section of the rotation shaft 303 toward the compressor wheel 304. The collar 306 is fixed to the rotation shaft 303. The bearing 307a has a tapered shape corresponding to the shape of the tapered portion 305 and having a slightly larger diameter than the tapered portion 305. The bearing 307b has a tapered shape corresponding to the shape of the collar 306 and having a slightly larger diameter than the collar 306.
The bearing 307a and the bearing 307b are aerostatic bearings. Pressurized air is supplied around the tapered portion 305 and the collar 306. This lifts the tapered portion 305 and the collar 306 above the bearing 307a and the bearing 307b, respectively, and thus the rotation shaft 303 rotates without generating friction with the bearings 307a, 307b. The gas pressure acts on the tapered surface of the tapered portion 305 and the tapered surface of the collar 306 in a perpendicular direction. The gas pressure acts not only in the radial direction but also in the thrust direction. Thus, the turbocharger 300 does not require a thrust bearing.
As illustrated in FIG. 13, Japanese Unexamined Patent Application Publication No. 58-196319 discloses an air bearing apparatus 500 including a rotation shaft 501, a bearing 503, another bearing 504, an air bearing 506, another air bearing 507, a flow passage 508, and another flow passage 509. The air bearing 506 is disposed between the rotation shaft 501 and the bearing 503. The air bearing 507 is disposed between the rotation shaft 501 and the bearing 504. The bearings 503 and 504 include the flow passages 508 and 509, respectively. Pressurized air is supplied to the air bearings 506 and 507 through the flow passages 508 and 509, respectively. The air bearings 506 and 507 each have a tapered shape and are disposed such that a larger-diameter portion of the air bearing 506 is placed opposite to a larger-diameter portion of the air bearing 507. Japanese Unexamined Patent Application Publication No. 58-196319 does not disclose the positional relationship between the air bearing apparatus 500 and an impeller to be attached to the rotation shaft 501.